Power supply unit



June 1, 1,937. R. B. MoKlNLl-:Y

POWER SUPPLY UNIT 10 Smeets-sheet 1 Filed March 8, 1935 II Q I N TLM@ Fig. Z.,

Ohmley ATTORNEY HIS R. B. MCKINLEY 2,082,168

POWER SUPPLY UNIT Filed March 8, 1935 l0 Sheets-Sheet 2 June 1, 1937.

INKENTOR Rezd. M Qh'mleg. BY Q22,

H15 ATTORNEY Fig. 9.

l0 Sheets-Sheet 5 R. B. M C Kl NLEY POWER SUPPLY UNIT Filed March 8, 1955 June l, 1937.

JNYENTOR Hmley A TTORNEY HIS Reid 5M? BY Y June l, 1937` R. B. MCKINLEY 2,082,168

POWER SUPPLY UNIT Filed March 8, 1955 l0 Sheets-ShamL 4 l INENToR Z y BeidBLMQIinZQy June 1, 1937. R. B, MCKINLEY 2,082,168

POWER SUPPLY UN 1T Filed March 8, 1935 lO Sheets-Sheet 5 j INVENT ffl; Held M inleg? 1.?

HIS ATTORNEY June 1, 1937. R. B. MCKINLEY POWER SUPPLY UNIT 1935 lO Sheets-Sheet 6 Filed March 8 QWN NWN NWN @l y mey E l. mr NZ M wrm m E www A M. s @m u 0 UnY B m June 1, 1937. R. B. MCKINLEY POWER SUPPLY vUNIT Filed March 8, 1935 l0 Sheets-Sheet 7 RE @QN t INVENTOR Rezdnlg/ BY LM HIS ATTORNEY www R. B. MCKINLEY June 1, 1937.`

POWER SUPPLY UNIT lO Sheets-Sheet 8 Filed March 8, y1935 l ,AM/

R. H m M El m Wm T IHNWA 0 Mlm uw? 9.00? .E B

R. BI MCKINLEY POWER SUPPLY UNIT Filed March 8, 1935 1o sheetssheet s June 1, 1.937.

June 1, 1937. R B, MCKINLEY 2,082,168

POWER SUPPLY UNIT Filed March 8, 1955 l0 Sheets-Sheet 10 167 I INVENTOR MQ/l'nleg 22 HIS f ATTORNEY Patented June 1, H537y UNITED` STATES PATENT OFFICE POWER SUPPLY UNIT Application March 8, 1935, Serial No. 10,087

10 Claims.

My invention relates to power supply units, and particularly to units which may be used in place of storage batteries as a source of substantially constant direct current for operating telephone exchanges, the relays and other devices included in centralized traic control systems for railroads, lights, motors, and the like. More particularly, my present invention relates to units of the type described in which alternating curm rent from a suitable source, after being stepped up or stepped down by a transformer to the proper potential for rectification, is rectified by asymmetric units of the copper oxide or dry disk type, and is then filtered by suitable filtering *l means.

One object of my invention is to provide a convenient self-contained unit of the type described which is not only compact and economical to manufacture but which is readily accessible o iur inspection, test, maintenance, or adjustment.

Another object of my invention is to provide a unit of the type described which will operate successfully on a wide range of alternating current voltages.

Other objects of my invention will appear as the description proceeds.

' I will describe several forms of units embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a front elevational view of a housing H containing two power supply units embodying my invention. Fig. 2 is a left-hand side View of the housing H shown in Fig. 1. Fig. 3 is a top plan view of the housing H shown in Fig. 1. Fig. 4 is an elevational view of the unit U1 which is mounted in the housing H, this unit being rotated in a clockwise direction through an angle of 90 from the position which it occupies in the housing. Fig. 5 is i) a view of the unit U1 as it appears when viewed from the lower side in Fig. 4. Fig. 6 is a view of the unit U1 as it appears when viewed from the right in Fig. 5. Fig. 7 is a detail view of a por- -tion of the unit U1 as it appears when viewed from the left in Fig. 4. Fig. 8 is a front elevational view of the base l of the unit U1 shown in Figs. 4, 5 and 6. Fig. 9 is a detail view showing a part of the base l as it appears during one step in the process of construction of the base. Fig. 10v is a wiring diagram for the unit U1 shown in Figs. 4, 5 and 6. Fig. 11 is a front elevational View showing another form of power supply unit embodying my invention, certain of the parts being broken away to better illustrate the construction thereof. Figs. 12 and 13 are left-hand side and right-hand side views, respectively, of the power supply unit shown in Fig. 10, certain of the parts in these views also being broken away to better illustrate the construction of the unit. Fig. 14 Ts a sectional View taken on the line XIV-XIV of Fig. 13. Fig. l5 is a detail View showing one of the rectifier stacks forming part of the power supply unit illustrated in Figs. 11 to 14, inclusive. Fig. 16 is a diagrammatic View illustrating the wiring diagram for the unit shown in Figs. 11 to 14, inclusive. Fig. 17 is a front elevational view showing another form of power supply unit emundying my invention, certain of the parts being broken away to better illustrate the construction thereof. Figs. 18 and 19 are left-hand side and right-hand side views, respectively, of the power supply unit shown in Fig. 17, each of these Views also having certain parts broken away for the sake of clearness. Figs. 20 and 2l are sectional views taken on the lines XX-XX and X-XI, respectively, of Fig. 19. Fig. 22 is a wiring diagram of the unit shown in Figs. 17 to 21, inclusive.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Figs. 1, 2 and 3, as here shown two power supply units U1 and U2 embodying my invention are mounted in a single housing H which also embodies my invention. The units U1 and U2 are similar, and it is believed, therefore, that a description of one will suffice for both.

Referring particularly to the unit U1 shown in Figs. 4 to 6, inclusive, this unit in the form here illustrated comprises a suitable base l upon which all of the other parts of the unit are mounted. The base l may be of any preferred construction, but as best seen in Fig. 8, this base in the form here shown comprises an outer rim Ia formed by cutting four spaced V-shaped notches in one leg of a straight piece of angle iron in the manner illustrated in Fig. 9, bending the other leg of the angle iron at the apex of the notches to form a rectangle, and then welding together the meeting edges of the one leg and the abutting ends of both legs so that the rim is, in effect, an integral rigid whole. The base also comprises two transverse straps Ib and l@ riveted or otherwise fastened at their ends to the opposite sides of the rim la in parallel spaced relation adjacent one end of the rim, and a longitudinal strap Id riveted intermediate its ends to the two straps lb and lc adjacent one side of the base.

One advantage of constructing the base in the manner just described is that the base is relaon the other' side of the windings.

tively light in weight and at the same time is extremely rigid. Furthermore, the cost of construction of the base is small.

Disposed at the left-hand end of the base I as viewed in Figs. 4 and 5 is a full-wave rectier A comprising, in the well-known form here illustrated, four stacks or legs a, b, c and d, each consisting of a plurality of rectifier disks 4 of the copper oxide variety assembled on, but insulated from, a supporting bolt 5. Interposed in each stack between adjacent disks are suitable conducting n.. bers as well as a plurality of fins E, the two end fins and the middle fin of each stack being provided with a radially extending apertured lug 6a. The ns 6 serve as a means for radiating the heat generated by the passage of current through the disks, and also as convenient terminals for making electrical connection with the disks. The stacks a, b, c and d are mounted in quadrature spaced relation in upright supports or end plates 'I and 8 provided with aligned holes through which the opposite ends of the bolts 5 extend, and are secured to the end plates by means of nuts 9 screwed onto the outer ends of the bolts. A metal member iii is mounted on one end of each bolt 5 between the associated stack and the adjacent end plate 8, and each of these members is provided with an outwardly extending lug Il)n which projects thro-ugh a hole in the end plate 8, as best shown in Fig. 5, whereby the stacks are prevented from turning relative to each other and to the end plates. Each end plate is provided at its sides and upper end with inwardly extendinglr stiffening flanges II and at its lower end with an outwardly extending flange I2. The rectifier is fastened to the base I by means of bolts I3 which extend through aligned holes formed in the flanges I2 and the horizontal portion of the rim Ia of the base I at opposite sides of the base, as clearly shown in Figs. 4 and 5.

Disposed at the right-hand side of the base I, as viewed in Figs. 4 and 5 is a transformer T, a terminal board i3, a reactor L, a plurality of condensers C1 and C2, three resistors R1, R2 and R3, and a fuse F.

The transformer T may be of any suitable type, but, as shown, this transformer comprises a shell type core I5, the middle leg of which is sourounded by a primary and two secondary windings. The primary and secondary windings are not visible in Figs. 4, 5 and 6, but are shown diagrammatically in the wiring diagram for the unit illustrated in Fig. 10 wherein they are designated by the reference characters TI, I8 and "IB, respectively. The core I5 rests on two horizontal straps Ila and I'Ib, one of which IIa is fastened at its ends to the legs of an inverted U-shaped bracket I 8a which partly surrounds the core I5 on one side of the windings, and the other of which I1b is fastened at its ends to he legs of an inverted U-shaped bracket I8b which partly surrounds the core I5 The straps IIa and IIb may be fastened to the associated brackets in any desired manner but, as here shown, the ends of the straps are provided with tongues 2G which extend through slots in the associated legs of the straps and are then bent downwardly. The lower ends of the bracket I8a are bolted to the rim IfL of the base I by means of bolts 2|, and the lower ends of the bracket I8b are bolted to the strap IC1 by means of bolts 22, and it follows, tl erefore, that the transformer T and the brackets to raise the terminal board to the desired height. The brackets 125 and 24 are secured to the rim i5L of the base I by means of rivets which pass through the rim and through inwardly extending feet formed on the lower ends of the brackets. Mounted on the terminal board are a plurality of terminal posts designated by the reference characters 2l to 38, inclusive, which terminal posts are connected by means of suitable wires with certain of the devices making up the unit U1, as will be more fully described hereinafter, and which serve to facilitate making external electrical connections with the unit, as will also more fully described hereinafter.

The reactor L in the form here shown comprises a winding 5S surrounding one leg of a rectangular laminated coi-e ib provided with one or more air gaps 4I. Four vertically disposed bolts 42 are fastened to the core iii adjacent the four corners `of the core by means of straps 43 and nuts 44, and the lower ends of these bolts extend through holes provided in the straps Ib and IC of the base I and carry nuts 4115, whereby the reactor is securely fastened to the base by means of the bolts.

The condensers C1 and C2 are fastened by means of lugs 45 and bolts il to a metal plate 48 which serves not only as a supporting plate for the condensers, but as a common connection for one terminal of the condensers, this connection being made through the lugs 15, bolts 41 and the cases of the condensers, these cases as here shown being metal. The supporting plate 48 is disposed directly above the reactor L and is fastened at one end to depending terminal posts 4S and 5i] (see Fig. 6) mounted in a terminal block 5I which is secured by means of bolts 52 to the underside of the bracket 24, while the ,other end of the supporting plate is secured to depending terminal posts 53 and 54 (see Fig. 7) mounted in a 'terminal block 55 which is secured by means ci bolts 5i) to the underside of the bracket 25. The terminal posts 49, 50, 53 and 54, in addition to serving as a support for the plate 48, also serve as junction points for numerous wires, as will be described more fully hereinafter. The condensers C1 and C2 are of the electrolytic type, and each has one plate connected to its case and the other plate to a terminal post 92 mounted in the upper end of the condenser.

The resistor R1 is secured by `means of terminal posts and 58 to a terminal block 60 which is bolted to the upper side of the bracket 24 by means of the same bolts which bolt the terminal block 5I to the bracket im, and the resistor R2 is secured to terminal posts 52 and 63 mounted in a terminal block which is bolted to the upper side of the bracket by means of the same bolts 55 which bolt terminal block 55 to the bracket 25.

The resistor R3 is secured by means of terminal posts 65 and to a terminal block di' 'which is bolted to the plate i8 by means of bolts ist.

The fuse F is of a well-known type Commonly lll :fil

used in telephone switchboar'ds, and as shown diagrammatically in Fig. l0 this fuse comprises a first conducting member 69 biased by its own resiliency to an upper position, and a second conducting member Ill biased by its own resiliency to a lower position, the two conducting members being connected at their free ends by a fusible member 1| which normally holds the first member in a lower position in opposition to its bias, and the second member in an upper position in opposition to its bias. In operation, the fuse is connected in the circuit which it is desired to protect by the fuse in such manner that the current flowing in this circuit will flow through the two conducting members and the fusible member, and if this current exceeds the rating of the fuse, the fusible member 1l will melt and will permit the conducting member 69 to move upwardly due to its bias, and the conducting member 10 to move downwardly due to its bias. The conducting member 69 usually carries a colored glass bead which is conspicuous when the mem.- ber occupies its upper position but not when this member occupies its lower position. The fuse F is mounted on a fuse block 13 which, as shown in Figs. 4 and 5, is secured to one end of a bracket 14, the other end of which is fastened to the bracket 25 by means of the bolts 56. The fuse block 13 is provided with a contact member 15 shown diagrammatically in Fig. 10, which member cooperates with the conducting member 10 in such manner that, when the conducting member moves to its lower position, it will engage the contact member 15 to close a contact lll-15.

It should be pointed out that, with the fuse and fuse block mounted in the position shown, the fuse, which is of relatively delicate construction, is protected from damage due to accidental bumping, and is at the same time clearly visible for inspection and readily accessible for replacement.

Referring now to Fig. l0, it will be seen that the primary 11 of transformer T is provided with terminal leads 11a and 11b and with a tap lead 11C, which leads are connected respectively with the terminal posts 21, 29 and 28 of terminal board B on the under side of the terminal board. In a similar manner, the secondary 18 of transformer T is provided with terminal leads 182L and 18b and with a tap lead 18C, which leads are connected respectively with the terminal posts 30, 32 and 3l of terminal board B on the under side of the terminal board, while the secondary 19 of transformer T is provided with terminal leads 192L and 'lllb and with tap leads 19C and 19d, which leads are connected respectively with the terminal posts 33, 35, 34 and 35 of terminal board B on the under side of the terminal board. It will be apparent, therefore, that, if a source of alternating current is connected with two of the terminal posts 21, 28 and 29, an alternating electromotive force will be available between each two of the terminal posts 33, 3| and 32 and also between each two of the terminal posts 33, 34, 35 and 36. It will also be apparent that by properly connecting different ones of the terminal posts 30, 3l and 32 with different ones of the terminal posts 33, 34, 35 and 35, all or part of either secondary winding of transformer T may be connected in series with all or part of the other secondary winding of transformer T in either an aiding or an opposing relation. The two secondary windings are so constructed that the electromotive forces which are available between the different terminal posts 30, 3l and 32 and between the different terminal posts 33, 34, 35 and 36 will all be different, and

it follows that by properly connecting' the two secondaries of transformer T together at these terminal posts, a large number of electromotive forces differing from each other by small increments may be obtained.

As shown in the drawings, the terminal posts 32 and 35 are connected together by a jumper 83, and the terminal post 3l is connected with one end of a wire 8l, while the terminal post 33 is connected with one end of a wire 82. It will be seen, therefore, that, as here shown, the portion of secondary 13 of transformer T between tap lead 18c and terminal lead `13b is connected in series with the portion of secondary winding 19 between tap lead 'ld and terminal lead 13a in such manner that the resultant electromotive force which is impressed on the wires 3! and 32 when current is supplied to the transformer T will be equal to the diiference between the electrornotive force which is induced in the indicated portions of the two secondary windings. Y

The free end of wire 32 is connected to the center fins 3 of the stacks a and b of rectifier A, and the free end of wire BI is similarly connected with the center n 3 of the stacks c and il of rectifier A. The upper nn 3 of stack a is connected by means of wires 83 and 33 with the upper iin 6 of the stacks b` and c, respectively, and the upper fin 'i of stack b is connected by means of wire tol the upper fin of stack d. lt will be seen, therefore, that the upper fins of the stacks a., b, c an-d d are all connected together. The lower fin 6 of stack a is connected by means of wires 83 and 81 with the lower 3 of stacks b and respectively, and the lower fin of stack b is connected by means of a wire 38 with the lower iin of stack d. It follows, therefore, that the lower ns of stacks a, b, c and d are also all connected together. The stacks a, b, c and d are each assembled in such manner that current will flow upwardly through these and with the stacks connected togetherl in the manner just described, if a load is connected to the upper and lower fins of the stacks when alternating current is being supplied to the wires 3| and 32, direct current will flow from the upper fins through the load to the lower fins in a manner which is well understood in the art.

rFhe upper n 5 of stack c is connected to one lead 89 of reactor L, and the other lead of this reactor is connected to the previously described terminal post B5. The lower rin il of stack c is connected by means of a wire 3l to the previously described terminal post 66. As was previously pointed out, the resistor R3 is constantly connected between the terminal posts t5 and t3, and it follows, therefore, that this resistor will maintain a constant load on the rectifier. This resistor has a relatively high resistance as compared with the resistance of the load and is provi-:led fer the purpose of improving the regulation of the unit when the external load on the unit is small.

The terminal 92 of the condenser C1 is connected to the terminal 92 of condenser C2 by means of a wire S3 and to the terminal post by means of a wire 94, the conducting member 63 of fuse F, fusible member 1l of fuse F, conducting member 1l) of fuse F, and a wire 35. The terminal posts 35 and 36 are connected by means of wires 96 and 31, respectively, to the terminal posts 3l and 33 of the terminal board B, which latter terminal posts are adapted to be connected to the load which is to be supplied with current by the unit U1. It will be apparent, therefore, that the reactor L and condensers C1 and C2 serve to smooth out the ripple in the current supplied by the rectifier to the external load in the usual and well-known manner.

It is desirable to be able to readily detect the failure of one of the condensers C1 and C2, and to accomplish this result the contact 10--15 of fuse F is utilized to control two indication lamps 08 and 99 which are secured to the housing H in which the unit U1 is mounted in a manner which I will describe hereinafter. The lamp 98 is provided With a circuit which may be traced from terminal post 65 through wire 95, conducting member 10 of fuse F, contact member 15, wire |00, terminal post 63, resistor R2, terminal post 62, wire |0|, lamp 98, and wires |02 and |03 to terminal post 66. The lamp 99 is similarly provided with a circuit which may be traced from terminal post 65 through wire 95, conducting member 10 of fuse F, contact member 15, wire |00, terminal post 63, wire |04, terminal post 58, resistor R1, terminal post 51, wire |05, lamp 99, and wire |03 back to terminal post 6E.

With the fuse F and lamps 98 and 99 arranged in the manner described, it will be seen that. as long as condensers C1 and C2 are functioning properly, the parts of fuse F will occupy the plo-- sitions in which they are shown in the drawings, and under these conditions, the circuits for both lamps 98 and 99 will be open at contact 1.0-15 of fuse F, so that both of these lamps will then be extinguished. However, if one of the condensers C1 or C2 becomes short circuited, the fuse F will then be connected with the terminal posts 65 and 66, and hence with the out-put terminals 31 and 38 of the unit U1, and the resultant current which will then iiow` through the fusible member 1| will melt this member and cause it to release the conducting members 59 and 10, thereby causing contact. 10-15 to close. When this contact becomes closed, the circuits for both lamps will then be completed and both lamps will become lighted. The lighting of these lamps will give an indication that one of the condensers is defective, and` the lamps will continue to burn until the defective condenser is replaced and a new fuse is inserted in place of the blown fuse.

It should be pointed out that the voltage available for lighting the lamps 98 and S9 is higher than the voltage in which lamps of the type which it is desired to employ are commercially available, and it is for the purpose of reducing the available voltage to the rated voltage of the lamps that the resistors R1 and l.2 are provided.

Referring now again to Figs l, 2 and 3, the housing I in which the units U1 and U2 are mounted comprises a framework consisting of four upright angle bars |06, |01, |00 and |09 riveted to the corners of the three horizontally disposed vertically spaced rectangular members H0, and H2, each constructed in the same manner that the rim IfL of the previously described base of the unit U1 is constructed. Attached to the back and two sides, respectively, of the frame are panel members H3, ||4 and ||5, each comprising a perforated sheet of metal having U-shaped` strips welded thereto at its edges to prevent the edges, which are necessarily rough, from scratching persons handling the panel member, and also to improve the appearance of the panel member and at the same time strengthen it. A panel member ||6 constructed in the same manner as the panels ||3, ||4 and ||5 is also attached to the top of the frame, and two other panel members ||1 and ||8 which are also similar in construction to the panel members I3,

||4 and ||5 are attached to the front of the frame. For reasons which will be made clear presently, it is desirable to be able to easily remove ani7 one of the panel members, and the panel members are accordingly fastened to the frame by means of tap bolts which are screwed into tapped holes provided in the sides of the rectangular members ||0, and ||2.

The unit U1 is fastened to the housing in the upper part of the housing by means of two spaced A,

horizontal straps 9 and |20 which are riveted at their opposite ends to the upright angle bars |01 and |08, and four bolts |'J.|, two of which pass through aligned holes formed in the upper end of the rim |a of the base l and in the strap H9, and the remaining two of which pass through aligned holes formed in the lower end of the rim |a of the base and in the strap |20. It will be seen, therefore, that the unit U1 may be readily removed from the housing H by merely removing the bolts |2I. The position of the unit U1 within the housing is such that, when the panel member ||1 is removed, ready access to the unit U1 may be had for inspection, maintenance, test, and the like.

The unit U2 is secured to the housing E in the lower part of the housing by means of two spaced horizontally disposed straps 122 and |23 and bolts M24 in the same manner that the unit U1 is fastened to the housing, and ready access to this latter unit may be had at all times by removing the panel member H8.

The previously mentioned indication lamps 9B and 09 for indicating the failure of the condensers C1 and C2 are mounted in suitable insulating sockets |25 and |20 which are fastened. to a plate |21 riveted to the angle bar |05. The soclets |25 and 20 are provided at their forward ends with bulls--eyes |23 and are disposed in such positions that, when the panel member l1 in place, these bulls-eyes will project through clearance holes provided in the U-shaped binding strip oi the panel member.

Two other indication lamps not shown are associated with the unit U2, and these lamps are mounted in sockets |30 and |31 secured to a plato |32 which is also riveted to the angle bar iiit ci the housing H. The sockets |30 and |3| are provided with bulls-eyes |28 which project through clearance holes formed in the U-shaped binding strip of the panel H0.

The incoming power wires and outgoing lead wires may be brought into, and led out of, housing H through holes drilled in a plate |34 which is secured to the upper side of the horizontal member H2.

Referring now to Figs. l1 to 14, inclusive, I have here shown another' power supply unit cnibodying my invention, which latter unit I h designated as a whole by the reference charac .,r U3. This unit is mounted in a housing H3 coni-- prising a framework consisting of four upright angle bars |40, MI, |42 and |43 riveted or otherwise secured to the corners of three vertically spaced horizontally disposed rectangular members |44, M5 and |46, each constructed in manner Similar to the previously described lirn l of the base of the unit U1. Attached to the top, back, and two sides of the framework of the housing H3 by means of tap bolts |40 which are screwed into screw-threaded holes formed in the rectangular members |04, |45 and |40 panel members |49, |50, |5| and |52, respectively, each consisting of a sheet of perforated metal of the proper size, having its edges bound by U-shaped CFI ' and an insulating washer lill.

strips welded or otherwise fastened thereto, the U-shaped binding strips being provided at suitable locations with clearance holes for the reception of the tap bolts. Two other panel members |53 and |54, similar in construction to the panel members |49, |55, |5| and |52 are secured to the rectangular members at the front of the framework by means of tap bolts |48 in the same manner that the panel members |49, |58, |5| and |52. are secured to the rectangular members. It will be seen, therefore, that any one of the panel members may be quickly and easily removed by unscrewing the associated tap bolts |48, thus facilitating ready access to any part of the interior of the housing H3.

Located in the lower part of the housing H3 is a rectifier unit, designated as a whole by the reference character A3. This unit in the forni here shown comprises twelve rectier stacks s1, S12. These stacks are all similar, and a description of one will therefore suffice for all. Referring particularly to the stack s1 shown in Fig. l5, this stack in the form here shown comprises a plurality of rectifier disks 4 assembled on a bolt 5 which passes through suitable openings in the disks, and which is separated from the disks by an insulating sleeve |55. Disposed on each side of each disk 4 is a thin layer |56 of an impressionable conducting material, and interposed at suitable intervals in the stack are spacer members |51 and fins |58. The ns |58 serve to radiate the heat generated by the passage of current through the disks, and certain ones of these fins also serve a means for making electrical connections with the disks. Those ns which serve only to radiate heat are in the form of squares having all four corners cut away, while the remaining fins are in the form of squares having only three corners cut away. The stack s1 is divided into eight groups of ve disks each, these groups being designated by the reference characters |55 to |65, inclusive. The disks are so arranged that the disks of each group are all stacked in the same direction, but that, the disks or adjacent groups are stacked in opposite directions. The ns are so arranged in the stack that a iin which serves as a connector is located at each end of each group of disks, and that those ns which are located between adjacent groups serve as a connector for the disks of both groups. The two fins at the opposite ends of each group are connected respectively, at the corners which are not cut away with bus bars |81 and disposed at diagonally opposite corners of the uns, these bus bars being bent inwardly at one end to form offset portions |61a and 955e, respectively, for a purpose presently to be described. Pressure is applied to the stack by means of nuts |59 and |10 screwed onto the ends of the bolt 5, and interposed between the nut 59 and the adjacent iin |58 is a spring washer |1| and an insulating washer i12, while interposed between the nut |15 and the adjacent iin is a metal member lil, a spring washer |13 The insulating washers i12 and |14 serve to insulate the ends ie stack from the bolt 5, while the spring wai .i ill and |13 tend to maintain a uniform pressure on the stacks. The function of the metal member iii will be made clear hereinafter. The upper bus bar i511 serves as the negative bus or the stack and the lower bus bar |58 as the positive b-us bar, and it will be apparent that between the two bus bars there are eight current paths, one formed by each of the eight groups of disks. The direction of current through the path formed by each group is indicated in the drawings by an arrow.

The stacks s1 to S12, comprising the rectiiier unit A3, are mounted in the housing E3 in the following manner. Two spaced horizontal straps |15 and |16 are secured to the rectangular member |45 on opposite sides of the center of this member, and two other spaced straps |11 and |18 are secured to the rectangular member |46 in Vertical alignment with the straps |15 and |15, respectively. Attached at their opposite ends to the aligned straps |15 and lll' in lateral spaced relation are two vertical brackets 19 and |80 (see Fig. 14), and attached at their opposite ends to the aligned straps |15 and |18 are two vertical brackets |8| and E88 similar to the brackets 19 and |88. The brackets |19 and |88 are located in the same vertical plane, and the brackets |8| and |82 are also located in the same Vertical plane. A fth vertical bracket |83 is secured at its opposite ends to the rectangular members |45 and |46 at the left-hand sides of these members, as viewed in Fig. l1, and a sixth vertical bracket |84, similar to the bracket |83, is secured at its opposite ends to the rectangular members |45 and |45 at the right-hand sides of these members, as viewed in Fig. ll. The bracket |83 is equally spaced from the two brackets |19 and |85, and is disposed in a plane which is parallel to the plane in which the brackets |19 and |80 are located, and the bracket |54 is likewise equally spaced from the brackets |8| and |82, and is located in a plane which is parallel to the plane in which the brackets |8| and |82 are located. The bracket |83 carries a plu rality of upwardly inclined arms l85 (see Fig. 12) and the bracket |84 likewise carries a plurality of upwardly inclined arms |55 (see Fig. 13). The arms |85 and |85 are disposed in pairs with the arms extending in opposite directions from the associated vertical brackets, and each of these inclined arms is fastened to the associated vertical bracket by means of a pair of machine screws |81 which pass through clearance holes in the associated arm and are screwed into tap holes provided in the associated bracket. Each inclined arm is provided at its outer end with a hole which aligns horizontally with a similar hole provided in one of the straps |15, itil, |8| or |82, and each pair of aligned holes receives the opposite ends of the bolt Ei of a different one of the stacks s1 to S12 in a manner which will be readily understood from an inspection of the drawings. Each inclined arm |55 and |85 is also provided with a second hole which receives the outwardly extending lug l52L of the metal member l provided on the associated stack, to prevent the stacks from turning. The stacks are secured to the associated vertical brackets and upwardly inclined arms by means of nuts |9| screwed onto the outer end of the bolts 5.

With the stack secured to the housing H3 in the manner just described, it will be apparent that each stack s may be removed from the housing without disturbing the remaining stacks by first removing the nut |9| from the associated bolt at the end of the bolt which passes through the associated vertical bracket, and then removing the inclined arm |85 or |86 to which the other end of the stack is fastened, from the associated vertical bracket, by backing out the associated machine screws |81.

Mounted on each bolt 5 between the associated nut |10 and the associated inclined arm |85 or |86 is an insulating plate |92 (see Fig. 15). Each plate |92 is provided with a hole through which the lug I0n on the associated member |0 passes,

whereby the insulating plate is held in a fixed relation with respect to the associated stack. Each plate |92 is also provided with two other holes which receive the offset portions |61a and |68a of the bus bars |'61 and |68 of the associated stack, thus providing a convenient means for holding the bus bars in a xed position to enable conductors to be soldered thereto.

Also located in the lower part of the housing H3 are four condensers C3, C4, C5 and CG, two of which C3 and C5 are fastened by means of lugs 46 and bolts 41 to the upper side of a U-shaped bracket |95, and the remaining two of which, C4 and C6 are fastened by means of lugs 46 and bolts 41 to the under side of the web of the U- shaped bracket |95 directly below the condensers C3 and C5, respectively, The U-sliaped bracket |95, in turn, is secured at one end to depending terminal post 49 and 50 mounted in a terminal block 5| which is bolted to the under side of the rectangular member at the forward side thereof, as viewed in Fig. 11, and at the other end to depending terminal posts 53 and 54 mounted in a terminal block which is bolted to the under side of the rectangular member |45 at the side opposite to the terminal block 5|.

Disposed in the upper part of the housing H3 is a transformer T3, a terminal board B3, a reactor L3 and a resistor R4.

The transformer T3 is similar to the previously described transformer T, and is secured by means of four bolts 202 to horizontal supporting members which, in turn, are secured at their ends to the rectangular member |45 at the front and back of this member. The bolts 202 are secured to the transformer T3 by means of nuts 203 and straps 204 in an obvious manner.

The terminal board B3 is similar to the previously described terminal board B and is fastened by means of bolts 205 (see Fig. 11) to the vertical legs of two L-shaped brackets 206, the horizontal legs of which are fastened to the rectangular member |45 at its forward side, the parts being so arranged that ready access to the forward side of the terminal board may be had by removing the panel |53 of the housing H3. Mounted on the terminal board B3 are terminal posts 21 to 38, inclusive.

The reactor L3 is similar to the previously described reactor L, and is fastened by means of bolts 42 to two horizontal supporting members 201, one of which, as viewed in Fig. 14, is bolted at one end to the rectangular member |45 by means of one of the bolts 52 which fasten the terminal block 5| to the rectangular member, and at the other end to the rectangular member |45 by means of one of the bolts |56 which fasten the terminal block 55 to the rectangular meinber. The other horizontal supporting member 201 is secured to the rectangular member 45 by means of bolts 208.

An insulating terminal block 209 provided with two terminal posts 2|0 and 2|| is secured to the strap |16 and one of the straps 201 at the forward side of the housing. The terminal posts 2|0 and 2|| are adapted to be connected with the leads of the reactor L, as will be more fully described hereinafter, and serve as a convenient means for making connections with the reactor, as will also be described more fully hereinafter.

The resistor R4 is of well-known construction,

and comprises an insulating tube 2|3, upon which resistance wire is wound, secured to two Z-shaped end plates 2|4 and 2|5 which also support a terminal board 2 |6 carrying terminal posts 2|1 and 2|8 which are connected to the ends of the resistance wire. The end plates 2|4 and 2|5 are fastened to the rectangular member |45 at the right-hand side thereof, as viewed in Figs. 1l and .1.4, by means of bolts 2|9 and 220.

Two sockets |25 and |26 containing indication lamps 08 and 99 are fastened to a plate |21 which is riveted to the angle bar |43. The sockets |25 and |26 are provided with bullseyes |28 which, when the panel |53 is in place, project through holes provided in the U-shaped binding strip of this panel. The function of these lamps will be made clear presently.

Two fuse blocks 13 are secured to the rectangular member |44 at the forward side thereof (see Fig. 11), and mounted in these fuse blocks are two fuses F2 and F3 similar to the previously described fuse F.

Referring now to the wiring diagram for the unit U3 shown in Fig. 16, it will be seen that the leads 11a, 11C, 113,183, 18,18b,19,193, 19c and 19b of transformer T3 are connected respectively to the terminal posts 21 to 36, inclusive, of terminal board B3 in the same manner that the corresponding leads of transformer T are connected to the terminal posts 21 to 36, inclusive, of terminal board B. Terminal posts 32 and 35 are connected together by the jumper 80, and terminal post 3| is connected to one end of each of two wires 225 and 226, while terminal post 33 is connected to one end of each of two wires 221 and 228. It will be seen, therefore, that, when primary 11 of transformer T is energized, an electromotive force will be impressed on wires 225 and 221 and also on wires 226 and 228, which electromotive force will be equal to the sum of the electromotive forces induced in the portion of secondary 18 between leads 18c and 18b and the portion of secondary 19 between leads 191L and 19C.

The free end of the wire 225 is connected to the positive bus bar |68 of stack 37, and the free end of wire 221 is connected with the positive bus bar |68 of stack S5. The positive bus bar |68 of stack s" is also connected by means of a wire 428 with the positive bus bar |68 of stack s3, and with the negative bus bars |61 of stacks s3 and s4, while the positive bus bar |68 of stack S5 is also connected by means of a wire 229 with the positive bus bar |68 of stack s6, and with the negative bus bars |61 of stacks s1 and s2. The positive bus bars of stacks s1, s2, s3 and s4 are all connected together by means of a wire 230, and the negative bus bars of stacks S5, s3, s3 and s3 are all connected together by a wire 23|. The free end of wire 226 is connected to the positive bus bar |68 of stack S12, and the free end of wire 228 is connected to the positive bus bar |68 of stack S11. The positive bus bars |68 of stacks S9 and S10 are connected together by a wire 232, and the negative bus bars of stacks S11 and S13 are connected. together by a wire 233. The positive bus bar |68 of stack s1 is also connected to a wire 234, and the negative bus bar |61 of stack S5 is connected to a wire 236, while the positive 2 bus bar of stack S9 is also connected with a wire 235 and the negative bus bar |61 of stack S11 with a wire 231.

With the stacks connected together', and connected with the wires 225, 221, 226 and 228 in Cia the manner just described, it will be readily understood that when the wires 225 and 221 are supplied with alternating current, the wires 234 and 233 will be supplied with rectified direct current by the stacks s1 to s3, inclusive, of rectier unit A3, and that, when the wires 223 and 223 are supplied with alternating current, the wires 233 and 23? will be supplied with rectified direct current by the stacks S9 to S11, inclusive, of the rectiiier unit A3.

The free ends of the wires 234 and 235 are connected to the terminal post 2 l il, and the free ends of the wires 233 and 237 are connected to the terminal post 53. Terminal post 2 I3 is also connected to one terminal of reactor L3, while terminal post 53 is also connected to terminal post 2 Il by means of a wire 238, and to terminal post 38 by means of a wire 233. The remaining terminal of reactor L is connected to terminal post 2l l, which latter terminal post is further connected to terminal post 3l by means of a wire 240, and to terminal post 228 by means of a wire 24|. It will be seen, therefore, that resistor R4 is connected in series with the winding of reactor L3 between wires 234 and 23"@` and also between wires and 23?, so that, when the wires 234, 236, 233 and 23T' are supplied with rectified current, the resistor R4 will maintain a constant load on the rectiiier. It will also be seen that, if an exterior load is connected to the terminal posts and 33, which terminal posts constitute the output terminals of the unit, the reactor L3 will be connected in series with this load between the wires 234 and 233 and between the wires 235 and 2.3i'.

The terminals 92 of the condensers C3 and C5 are connected together by a wire 242, and the terminal 92 of condenser C5 is also connected to the terminal post 2 l 3 by means of a wire 243, the conducting member 33 of fuse F3, fusible member 'ii of fuse F3, conducting member 'l0 of fuse F3, and wire 244. The terminals 92 of condensers C4 and C are likewise connected together by a wire and the terminal 92 of condenser C3 is further connected to the terminal post ZIB by means of wire 243, conducting member 69 of fuse F2, fusible member 'il of fuse F2, conducting member i@ of fuse F2, and wires 243 and 244 to terminal post 2.!8. It will be seen, therefore, that the condensers C3 and C5 are connected in parallel, and are included in a branch circuit which may be traced from terminal post 3l through wires 2M and 244, conducting member 18 of fuse F3, fusible member il of fuse F3, conducting member 33 oi fuse F3, wire 243, condensers C3 and C5 in parallel, bracket E35, terminal post 53, and wire 233 to terminal post 38. It will also be seen that the condensers C4 and C6 are connected in paraiiel, and are connected in a circuit which may be traced from terminal post 3l through wires 243, 244 and 241, conducting member 'l0 of fuse F2, fusible member 1l of fuse F2, conducting member 33 of fuse F2, wire 243, condensers C4 and C3 .in parallel, bracket 35, terminal post 53, and wire to terminal post 38. It follows that ie condensers C3, C4, C5 and C3 are all connected in parallel with any load which may be connected with terminal posts 3i and 33 and also with the resistor R4. It also follows that, if either one of the condensers C3 or C5 should fail, the fuse F3 will then be connected directly across the output terminals 3l and 38, and under these conditions fusible member 'il will blow and cause the fuse to close its contacts l0- 15. Likewise, if one oi the condensers C4 or C6 should become shortcircuited, the fuse F2 will then be connected directly across the output terminals 3l and 38, and under these conditions the fusible member 'H of fuse F2 will blow and cause the fuse F2 to close its contact lil-lil,

When contact lll-'i5 of fuse F2 becomes closed, a circuit is completed for the lamps 98 and 99 passing from terminal post 2 i3 through wires 244 and 262, contact 'iti-l5 of fuse F2, wires 252 and the lamps 38 and 99 connected in multiple, and wire to terminal post 2H. In a similar manner, when contact 'iiil5 of fuse F3 becomes closed, it completes another circuit for the lamps 33 and 39, which latter circuit may be traced from terminal post 212 through wire 244, contact iiii3 of fuse F3, wire 250, the lamps 38 and 99 in parallel, and wire 25| to terminal post 2H. When either one of the circuits just traced becomes closed, the lamps 98 and 99 will become lighted, thereby indicating that one or more of the condensers C3, C4, C5 or C6 has become shortcircuited. After the lamps 98 and 99 have once become lighted, th ey will remain lighted until the defective condenser is replaced and a new fuse is provided to replace the fuse which became blown due to the defective condenser.

Referring now to Figs. i7 to 2l, inclusive, I have here shown still another form of power supply unit embodying my invention, this latter unit being designated as a whole by the reference character U4 and being mounted in a housing H4. The housing H4 is similar to the previously described housing I-i3 with the following exceptions: The height of the housing H4 has been increased to accommodate additional rectifier stacks, as will be made clear hereinafter, and in order to provide the housing with the necessary additional strength and to facilitate the mounting of the additional stacks in the housing, an additional rectangular member, designated by the reference character 233, has been provided. Furthermore, the lengths of the side and back panels have been increased an amount corresponding to the increased height of the housing, and the front of the housing, instead of being closed by two panels, as is the case of the housing H3, is closed by means of three panels, the top and bottom ones of which are the same size and shape as the panel 454 of the housing H3.

Disposed in the upper part of the housing H4 is a. group of sixteen rectifier stacks, each designated by the reference character s with a suitable distinguishing exponent, and disposed in the lower part of the housing H4 is another group of sixteen rectifier stacks, each of which is also designated by the reference character s with a suitable distinguishing exponent. Each stack s is similar to the previously described stack s1, and the stacks of each group are mounted in the housing H4 in the same manner that the previously described stacks s1 to S32 are mounted in the housing H3.

Disposed in the housing H4 between the two groups of rectier stacks are a transformer T4, a terminal board B4, a reactor L4, twelve condansers C3 to C19, inclusive, a resistor R5, and 'four fuses F4, F5, F3 and Fl.

The transformer T4 is of the same general type as the previously described transformer T, but

a somewhat larger capacity than the transformer T, and has its core laininations bolted together by means of bolts 232 which extend through aligned holes in the laminations, one bolt, as here shown, being located near each corner of the core. Secured to the opposite sides of the transformer core near the bottom of the core, by of the two lower bolts 262, are two angle brackets F63. The core o the transformer' rests its opposite ends on two transformer supports 264 and 263 which are secured at their opposite ends to the rectangular member |45, and the angle brackets 263 are apertured to receive the Shanks of stud bolts 266, the screw-threaded ends of which are screwed into tap holes provided in the transformer supports, whereby the transformer is rigidly fastened to the housing H4.

The terminal board B4 is similar to the previously desc be terminal board B, and is secured to the rec gular member |45 in the same manner that the terminal board B3 is secured to the rectangular nernber |45. The terminal board B4 has mou d thereon terminal posts 21 to 38, inclusive. terminal post 261.

The reactor L4, as here shown, comprises two E-shaped laminated core sections 26Ba and 269b clamped together with their legs in spaced relation, by means oi two clamping plates 269 and four bolts 213 which extend through aligned holes provided in the corners of the clamping plates, the proper spacing between the legs being maintained by non-magnetic spacing members in a Well-known manner. The reactor L1 also comprises a winding 21| which surrounds the confronting middle legs of the two core sections. To facilitate the making of electrical connections with the winding 21|, the terminal leads of the winding are secured to two terminal posts 212 and 213, mounted in a terminal block 214 which is bolted to the upper edge of the one clamping plate 269. Four feet 215 are bolted to the reactor its lower corners by means of the two lower bolts 213, and these feet are secured by means of tap bolts 216 (see Fig. 2l) to two straps 211, which straps, in turn, are secured to the rectangular member |45, thus securing 4the reactor to the housing H4.

The condensers C8, C9 and C10 are bolted to one side of the web of a U-shaped bracket 218 by means of lugs 46 and bolts 41, and the condensers C11, C12 and C13 are bolted to the other side of the web of the bracket 218 in axial alignment with the condensers C10, C9 and C8, respectively, by means of lugs 46 and the same bolts 41 which risen the condensers Ca, C9 and C1o to the bracket 218. One end of the bracket 218 is fastened to two terminal posts 219 and 280 mounted in a terminal block 28! which is bolted to the angle bar |4|, and the other end of the bracket 213 is fastened at two other terminal posts 232 and 233 mounted in a terminal block 294 which. is bolted to the angle bar |42. In a similar manner, the condensers C14, C15 and C16 are bolted to one side of the web of a Ushaped bracket 231 by means of lugs 46 and bolts 41, arri the condensers C17, C1B and C19 are bolted to the other side of the web of the bracket 281 in axial alignment with the condensers C14, C15 and C16, respectively, by means of lugs 46 and the same bolts t1 which fasten the condensers C11, C15 and C1G to the bracket 281. One end of the bracket 281 is fastened at two terminal posts 283 and 239 mounted in a terminal block 290 which is bolted to the angle bar |43, and the other end of the bracket 281 is fastened to two terminal posts 5:92 and 293 mounted in a terminal block 296 which is bolted to the angle bar |49. It will noted that the bracket 21B is disposed directly above the transformer T4, while the bracket 281 is disposed directly above the reactor L4.

Resistor R5 is secured to the rectangular member |45 of the housing H4 at the forward side thereof, between the transformer T and reactor L, by means of an L-shaped bracket 295.

The fuses F5, F4, F0 and F1 are all similar to the previously described fuses F, and are each mounted on fuse blocks 13, which fuse blocks, in turn, are bolted to the under side of the rectangular member 269 of the housing H4 at thc forward side of the rectangular member.

Referring now to the wiring diagram for the unit U4 shown in Fig. 22, it will be seen that the leads 11a, 11C, 11b, 18, 18C, 1811, 19e, 19, 19d and 191J of transformer T1 are secured respectively to the terminal posts 21 to 36, inclusive, of terminal board B. It will also be seen that the secondary winding 1B of transformer T1, as here shown, is provided with an additional tap lead 18d, which tap lead is secured to the terminal post 261 oi terminal board B. The terminal posts 32 and 35 are connected together by a jumper 00, and the terminal post 261 is connected to two wires 296 and 299, while the terminal post 33 is connected to two wires 300 and 30|. It will be seen, therefore, that when the primary 11 of transformer T is energized, an electromotive force will be impressed between the wires 298 and 300, and also between the wires 299 and 30|, which electromotive force will be equal to the sum of the electromotive forces induced in the portion of 1 the secondary 1li of transformer T1 between the' leads 131a and 18d and in the portion of the secondary 19 of transformer T1 between the leads 19d and 19e.

The wires 298 and 300 are respectively connected at their free ends with the bus bar |68 of stack S20 and with the bus bar |61 of stack and the bus bar |68 of stack S20, in turn, is connected with the bus bar |68 of stacks S11, S18 and S19 by means of a wire 309, and with the bus bar |61 of stacks S13, S14, S15 and S16 by means of wires 3|1 and 308, While the bus bar |61 of stack S21 is connected with the bus bar |61 of stacks S21, 322 and S23 by means of a wire 3|2, and with the bus bar |68 of stacks S25, S25, 321 and S28 by means of wires 3|8 and 3 I3. The bus bars |61 of stacks S17, S13, S19, S20, S25, S26, S27 and S28 are .all connected together by wires 3|0, 3|4 and 3|5, and the bus bars |68 of stacks'SlS, S14,

mi Si. r

S15, 516, S21, 322, S23 and S24 are all connected together by wires 3D1, 3|6 and 3|| in the manner shown. The bus bar |61 of stack s2 is further connected to one end of a wire 3|9, and the bus bar |68 of stack 324 is further connected to one end of a wire 320. The wires 3|9 and 320 constitute the output wires for the group of stacks S13 to S211, inclusive, and it will be apparent that when the wires 293 and 30|) are supplied with alternating,r current in the manner previously described, the wires 3|9 and 320 will be supplied with rectified direct current.

The wires 299 and 30| are respectively connected at their free ends with the bus bar |68 of stack 333, and with the bus bar |61 of stack S37, and the bus bar |68 of stack S33, in turn, is connected with the bus bars |68 of stacks S34, S35 and S35 by means of a wire 32|, and with the bus bars |51 of stacks S29, S30, S31 and S32 by means of wires 322 and 323, while the bus bar i6? of stack S31 is connected with the bus bars of stacks S33, S39 and S40 by means of a wire and with the bus bars |68 of stacks S41, S42, S13 and 511 by means of wires 325 and 326. The bus bars |61 of stacks S33, S34, S35, S35, S41, S42, .S43 and 544 are all connected together by wires 321, 328 and 329, and are also connected with one end of a wire 330, and the bus bar |68 of stacks S29, S30, S31, S32, S37, s55, 339 and s4o are connected together by wires 33|, 332 and 333, and are also connected to one end of a wire 334. The wires 330 and 334 constitute the output wires for the stacks $29 to 344, and it will be apparent that these wires will be supplied with rectified direct current by the stacks S29 to S44 when the wires 299 and 38| are supplied with alternating current.

The free ends of wires 3|9 and 330 are connected to terminal post 2|8, and the free ends of wires 328 and 334 are connected to terminal post 212. The terminal post 2|8 is also connected to one end of resistor R5, and to terminal post 38 by means of a wire 3313, and the terminal post 212 is also connected to one terminal of reactor L4, as was pointed out hereinbefore. The other terminal of reactor L is connected to terminal post 213, which latter terminal post is also connected to terminal post 2|1 by means of a wire 338, and to terminal post 31 by means of a wire 331. Terminal post 211 is, of course, connected to the opposite terminal of resistor R from terminal post 2 8. It will be seen, therefore, that, if a load is connected with the terminal posts 31 and 38, one-half the load current will be rectified by the one group of stacks and the other half of the load current will be rectified by the other group -oi stacks, and that the total load current will flow through the reactor L4. It

-will also be seen that resistor R4 constitutes a constant load on both groups of stacks.

The condensers C11, C9 and C10 are connected i in parallel and are included in a branch circuit which may be traced from terminal post 38 through wire 336, terminal post 218, wire 335, terminal post 28D, bracket 283, condensers C8, C9 and C10 connected in parallel, wire 348, conducting member 69 of fuse F4, fusible member 1| of fuse 154 conducting member 18 of fuse F4, wires 34|, 342 and 343, terminal post 2|1, and Wires 338 and 331 to terminal post 31. The condensers C11, C12 and C13 are likewise connected in parallel and are included in a branch circuit which maybe traced from terminal post 38, through wire 336, terminal post 2|8, wire 335, terminal post 280, bracket 288, condensers C11, C12 and C13 in parallel, wire 344, conducting member 69 of fuse F5, fusible member 1| of fuse F5, conducting member of fuse F5, wires 342 and 343, terminal post 2|1, wire 338, terminal post 213, and wire 331 to terminal post 31. The condensers C14, C15 and C16 are also connected in parallel and are included in a circuit which may be traced from terminal post 38 through wire 336, terminal post 2|8, wire 335, terminal post 280, wire 345, terminal post 288, bracket 281, the condensers C14, C and C16 in parallel, wire 348, conducting member 69 of fuse F5, fusible member 1| of fuse F6, conducting member 10 of fuse F5, wire 343, terminal post 2|1, wire 338, terminalpost 213, and wire 331 to terminal post 31. The condensers C17, C18 and C19 are further connected in parallel, andare included in a branch circuit which may be traced from terminal post 38, wire 33B, terminal post 2|8, wire 335, terminal post 280, wire 345, terminal post 288, bracket 281, condensers C17, C18 and C19 in parallel, wire 341, conducting member 69 of fuse F1, fusible member 1|, conducting member 18 of fuse F", wires 348 and 343, terminal post 3| 1, Wire 338, terminal post 213, and wire 331 to terminal post 31. It will be seen, therefore, that the condensers C8 to C17 are connected in parallel with any load which is connected to the terminal posts 31 and 38 of terminal board B4. It will also beseen that if one o the condensers C8, C9 or C1o becomes short-circuited, fuse F4 will blow, if one of the condensers C11, C12 or C13 becomes short-circuited, fuse F5 will blow, if one of the condensers C14, C15 or C16 becomes short-circuited, fuse F6 will blow, and if one of the condensers C17, C18 or C19 becomes short-circuited, fuse F7 will blow.

The indication lamps 98 and 99 are connected in four parallel circuits, each of which is controlled by one of the fuses F4. The circuit for the lamps 98 and 99 controlled by fuse F4 may be traced from terminal post 2|1 through wires 343, 342 and 34|, contact 10-15 of fuse F4, wires 349, 358, 35| and 352, lamps 98 and 99 in parallel, wires 353 and 345, terminal post 280, and wire 335 to terminal post 2|8. Each of the other circuits for the lamps 98 and 99 are similar to the circuit just described and will be apparent from an inspection of the drawings without describing them in detail.

With the lamps 98 and 99 controlled by the fuses in the manner just described, it will be seen that when any one of these fuses becomes blown due to one of the condensers C8 to C19, inclusive, becoming short-circuited, the lamps 98 and 99 will become lighted, thereby indicatingI that one of the condensers has become shortcircuited. When the lamps 98 and 98 become lighted, they will subsequently remain lighted until the defective condenser is replaced by a new one and a new fuse is provided in place of the blown fuse.

Although I have herein shown and described only a few forms of power supply units embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without Ideparting from the spirit and scope o my invention.

Having thus described my invention, what I claim is:

l. In a power supply unit including a rectifier for supplying rectified direct current to a load from a source of alternating current, and filtering means including a condenser adapted to be connected in parallel with the load, in combination, a fuse comprising two conducting members at least one of which is biased to one position but is held in another position by a fusible member which connects the two members, a contact member adapted to be engaged by said one conducting member when said one conducting member is moved to its one position, means for connecting said condenser in parallel with said load over a circuit including said two conducting members` and said fusible member of said fuse, an indication means, and means controlled by the contact formed by said one conducting member and said contact member for connecting said indication means in parallel with said load, whereby if said condenser becomes shortcircuited said fusible member will blow and permit said contact to close, thereby interrupting the circuit for the condenser and completing the circuit for the indication means.

2. In combination with a power supply unit including a rectifier for supplying rectified current to a load from a source of alternating current, a plurality of fuses each comprising two conducting members at least one of which is biased to one position but is normally held in another position by a fusible member which coniii nects the two members, a Contact member associated with each fuse in such manner that if the one conducting member of the associated fuse moves to its one position it will engage the associated Contact member and thereby close a Contact comprising the one conducting member and the contact member, a plurality of conden sers, means for connecting each of said condensers in parallel with said load over a circuit including the two conducting members and the fusible member of a diiierent one of said fuses, an indication lamp, and a plurality of circuits for connecting said lamp in parallel with said load cach including the contact associated with a different one of said fuses.

3. In combination with a power supply unit including a rectifier for supplying rectified direct current from a source of alternating current, a plurality of condensers arranged in groups, the condensers of each group being connected in parallel, a plurality of indicating devices one associated with each group of condensers, a fuse associated with each group of condensers, each said fuse comprising two conducting members each biased to one position but each held in another position by a fusible member which connects the two conducting members, a contact member associated with each fuse and arranged to cooperate with the one conducting member of the associated fuse in such manner that the one conducting member will engage the contact member to close a contact if the one conducting member moves to its biased position; means for connecting the condensers of each group, connected in parallel, in parallel with said load over a circuit including the two conducting members and fusible member oi a different one of said fuses; an indication lamp, and a plurality of circuits for said lamp each including the contact associated with a different one of said fuses and each arranged to be supplied with current from the rectifier when the associated contact is closed.

4. In a power supply unit of the type including a transformer secured to a supporting framework, a rectifier secured to said framework and receiving alternating current from said transformer and adapted to supply direct current to a load, and a reactor secured to said framework and adapted to be connected in series with the load, the combination of a pair of spaced terminal blocks secured to said framework, terminal posts mounted in said terminal blocks, a bracket mounted on said terminal posts, two filter condensers disposed on opposite sides of said bracket, lugs secured to each of said condensers and aligning with the lugs secured to the other condenser, and bolts extending through the aligned lugs and said bracket to fasten said condensers to said brackets, said condensers being adapted to be connected in parallel with the load to which current is supplied by the unit to reduce the ripple in the current.

5. A rectiiier stack comprising a bolt, an insulating sleeve surrounding said bolt, a plurality of rectier disks assembled on said sleeve, a thin layer of impressionable conducting material disposed on each side of each disk, a plurality of spacers interposed at intervals in said stack, a plurality of rectangular ns interposed at intervals in said stack, certain of said Iins having all four corners cut away and certain other of said uns having only three corners cut away, nuts screwed onto the ends of said bolt to apply pressure to said stack, insulating washers interposed in said stack between said nuts andl the adjacent elements oi the stack to insulate the elements oi the stack from the bolt, said disks being arranged in groups in said stack with the disks of each group all disposed in the same direction and with the disks of opposite groups disposed in opposite directions, and said fins being arranged in said stack in such manner that a n with only three corners cut away is disposed between each two adjacent groups and at each end of the two end groups, and bus bars disposed at diagonally opposite corners of the fins and extending through holes provided in the remaining corner of those ns which have only three corners cut away and electrically connected with the associated iins at the corners, the bus bars being connected to the fins in such manner that each group of disks provides a current path from the one bus bar to the other bus bar.

6. In a power supply unit in combination, a housing, two spaced brackets mounted in said housing in the same plane, a third bracket mounted in said housing, said third bracket being equally spaced from the other two brackets and being disposed in a plane which is parallel to the other two brackets, a plurality of arms secured to said third bracket by means of stud bolts passing through clearance holes in the associated arm and screwed into tapped holes provided in the bracket, said arms being disposed in spaced pairs with the arms of each pair extending away from each other, each said arm being provided with a hole which aligns with a hole in one or the other of the other two brackets, a plurality of rectier stacks each including a clamping bolt and each disposed with one end of the associated bolt extending through the hole in a different one of said arms and with the other end of the bolt extending through the hole which aligns with the hole through which the one end of the bolt extends, and nuts screwed onto the ends of said bolts.

7. In a power supply unit in combination, a housing, two spaced brackets mounted in said housing in the same plane, a third bracket mounted in said housing, said third bracket being equally spaced from the other two brackets and being disposed in a plane which is parallel to the other two brackets, a plurality of arms secured to said third bracket by means of stud bolts passing through clearance holes in the associated arm and screwed into tapped holes provided in the bracket, said arms being disposed in spaced pairs with the arms of each pair extending away from each other, each said arm being provided with a hole which aligns with a hole in one or the other of the other two brackets, a plurality of rectifier stacks each including a clamping bolt and each disposed with one end of the associated bolt extending through the hole in a different one of said arms and with the other end of the bolt extending through the hole which aligns with the hole through which the one end of the bolt extends, nuts screwed onto the ends of said bolts, and a plurality of members, one mounted on the bolt of each of said stacks at the end adjacent the associated arm and each provided with a lug which extends through a hole provided in the associated arm, whereby the stacks are prevented from turning relative to the brackets.

8. In a power supply unit in combination, a housing, two spaced brackets mounted in said housing in the same plane, a third bracket mounted in said housing, said third bracket being equally spaced from the other two brackets and being disposed in a plane which is parallel to the 

